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Nanomaterials (Basel). 2018 Nov 7;8(11). pii: E915. doi: 10.3390/nano8110915.

Light-Tuned DC Conductance of Anatase TiO₂ Nanotubular Arrays: Features of Long-Range Charge Transport.

Author information

1
Physics Department, Yuri Gagarin State Technical University of Saratov, 77 Polytechnicheskaya str., Saratov 410054, Russia. zimnykov@mail.ru.
2
Precision Mechanics and Control Institute of Russian Academy of Sciences, 24 Rabochayastr., Saratov 410024, Russia. zimnykov@mail.ru.
3
Physics Department, Yuri Gagarin State Technical University of Saratov, 77 Polytechnicheskaya str., Saratov 410054, Russia. vasilk.mikhail@yandex.ru.
4
Saratov Branch of Kotelnikov Institute of Radio-Engineering and Electronics of Russian Academy of Sciences, 38 Zelenaya str., Saratov 410019, Russia. vasilk.mikhail@yandex.ru.
5
Physics Department, Yuri Gagarin State Technical University of Saratov, 77 Polytechnicheskaya str., Saratov 410054, Russia. yuv-sergej@yandex.ru.
6
Physics Department, Yuri Gagarin State Technical University of Saratov, 77 Polytechnicheskaya str., Saratov 410054, Russia. alexspb88@mail.ru.
7
Institute of Microstructure Technology, Karlsruhe Institute of Technology, 1 Hermann-von-Helmholtz Platz, 76344 Eggenstein-Leopoldshafen, Germany. martin.sommer@kit.edu.
8
Physics Department, Yuri Gagarin State Technical University of Saratov, 77 Polytechnicheskaya str., Saratov 410054, Russia. vsysoev@sstu.ru.

Abstract

Experimental results related to the photoactivated dc conductance of anatase TiO₂ nanotubular arrays (aTNTAs) under pulsed irradiation by a laser light inside and outside the fundamental absorption band are presented. It is found that the mobility and diffusion coefficients of charge carriers in the examined aTNTA are extremely low due to a strong charge-phonon coupling, abundance of shallow traps, and hopping conductivity between adjacent nanotubes. We consider that the confining electric field appeared within the array structure due to the difference in the local concentrations of excess electrons and holes at large values of the dc conductance suppresses the drift current. In this case, the dc conductance of such aTNTAs is mainly matured by the diffusion of mobile carriers. A recurrent kinetic model for evolution of the dc conductance of aTNTAs under laser irradiation has been proposed to interpret the experimental results.

KEYWORDS:

Urbach energy; anatase nanotubes; charge mobility; dc conductance; diffusion current; drift current; inter-band transition; laser irradiation

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